On a recent Sunday, scores of families showed up at the Catholic Church of Nuestra Señora de la Merced in a working-class neighborhood of this vibrant port city.
They came not to attend services, but for a distinct purpose: to give blood for possible DNA matches with human remains recently unearthed in a suspected dumping ground for murder victims on the northern fringes of Veracruz. Police technicians were taking the blood samples.
All of those at the church said they were keen to identify loved ones who are among Veracruz’s legions of desaparecidos, or disappeared.
“I would say 80% of the families in Veracruz have a relative who is...